A group of 24 pregnant rhesus monkeys have been maintained on one of 3 purified diets throughout pregnancy. One diet was restricted in protein, one deficient in both protein and calories and one was the control diet. The monkeys were delivered at 158 days of gestation by cesarean section. The fetuses were killed at time of delivery and all organs weighed and anthropometric measurements taken. The fetal tissues have been studied by the various investigators. The data from these studies is now being statistically analyzed and results will be reported in the near future. Preliminary analysis of anthropometric data does not show significant differences between the fetuses taken from mothers on various diets. Furthermore, no obvious differences have been found in the neuronal development of the fetuses. The nutritionally deprived female monkeys will be continued on their respective diets and studies for immunological responses to various antigens carried out.